Enhancing Natural Attenuation through Bioaugmentation with Aerobic Bacteria that Degrade Cis-1,2-Dichloroethene, Chesapeake, Virginia

Site Name:

Site 21, St. Julien's Creek Annex (SJCA)

Location:

Chesapeake, Virginia

Period of
Operation:

Field activities were conducted from September 15, 2008 through May 23, 2009.

Cleanup
Type:

Field Demonstration

Technology:
Bioaugmentation

A bacterial culture consisting of an aerobic bacterium, Polaromonas sp. strain JS666, was used to treat groundwater contaminated with cis-1,2-dichloroethene (cDCE) and other chlorinated hydrocarbons. Details about the demonstration are provided below:

  • The field demonstration involved the construction of four test plots.
  • Plot #1: Bioaugmentation plot receiving JS666, oxygen, and buffer
  • Plot #2: Bioaugmentation plot receiving JS666 and buffer
  • Plot #3: Control plot receiving buffer
  • Plot #4: Control plot receiving oxygen and buffer
  • The monitoring network for each plot consisted of one injection well and seven monitoring wells placed upgradient, transgradient, and downgradient of the injection well.
  • The control plots included one injection well and two downgradient monitoring wells, located upgradient and transgradient to the plots. Two wells, located upgradient from the plots, served as background controls and received no amendments.
  • The strain JS666 is inactive below a pH of 6.5. To raise the groundwater pH to around 7.2, a phosphate buffer consisting of potassium monobasic orthophosphate (KH2PO4) and potassium dibasic orthophosphate (K2HPO4) was added once a month to the injection well of each test plot.
  • Two bioaugmentation events were performed during the demonstration. During the first bioaugmentation event on October 29, 2008, approximately 8 liters (L) of the culture, at a density of 1.8 X 109 colony forming units (CFU) per milliliter (ml), was added to each test plot. In addition, a total of 2,000 ml of phosphate buffer was added to help maintain the pH of the groundwater around neutral. During the second bioaugmentation event on February 25, 2009, 9 L of culture, at a density of 2.3 X 109 CFU/ml, was added to each test plot along with a total of 1,700 ml of buffer.
  • Starting in February 2009, to further enhance biodegradation, the extracted groundwater from all four plots was oxygenated to achieve a dissolved oxygen (DO) concentration just below 10 mg/L.

Cleanup Authority:
Department of Defense (DoD)

Contacts:

Principal Investigator
Patrick Evans
CDM
14432 S.E. Eastgate Way, Suite 100
Bellevue, WA 98007
Phone: 425-519-8300
Email: evanspj@cdm.com

Co-Principal Investigator
Rachel Brennan
The Pennsylvania State University
Department of Civil and Environmental Engineering
University Park, PA 16802
Phone: 814 -865-9428
Email: rbrennan@engr.psu.edu

Site Owner
Rodney Fricke
Aerojet-General Corp. P.O. Box 13222, MS-5519
Sacramento, CA 95813
Phone: (916) 355-5161
Email: rodney.fricke@aerojet.com

Site Regulator
Alexander MacDonald
California Regional Water Quality Control Board
11020 Sun Center Drive
Suite 200 Rancho Cordova, CA 95670
Phone: 916-464-4625
Email: amacdonald@waterboards.ca.gov

Environmental Restoration Program Manager
Andrea Leeson
ESTCP Office
901 Stuart Street, Suite 303
Arlington, VA 22203
Phone: 703-696-2118
Email: andrea.leeson@osd.mil

Contaminants:
Cis-1,2-Dichloroethene (cDCE)

Waste Source:
Various chlorinated hydrocarbons were released at the site due to dumping of solvents and chemicals used for dust and weed control and the presence of two abandoned leaking underground storage tanks (USTs).

Type/Quantity of Media Treated:
Groundwater (quanity not documented)

Purpose/Significance of Application:
The primary goal of this first field demonstration was to evaluate the effectiveness of JS666 for the in situ biodegradation of cDCE and other chlorinated ethenes/ethanes.

Regulatory Requirements/Cleanup Goals:
The cleanup goal was to decrease cDCE concentrations to below the maximum concentration limits (MCL) of 70 micrograms per liter (µg/L). The primary performance criteria for the demonstration included:

  • Achieve a greater than 75 percent reduction of cDCE concentration in groundwater in the bioaugmented plots
  • Reduce cDCE concentrations in groundwater in bioaugmented plots by two orders of magnitude compared to control plots.
  • Demonstrate growth and spatial distribution of JS666 away from the injection wells and achieve higher numbers of JS666 bacteria in bioaugmented plots than in control plots.
  • Show higher activity and higher numbers of JS666 bacteria in bioaugmentation plot with oxygen.

Results:
Sampling results from the demonstration indicated the following:

  • While a reduction in cDCE concentration was observed in the bioaugmented plots compared to the control plots, it was not twice that of the control plots. This was attributed to the lack of oxygen and high levels of TCE in some of the bioaugmented plots. As a result, the percent reduction of cDCE was less than the goal of a 75% reduction compared to baseline concentrations. Average cDCE concentrations were reduced by up to 44% in the bioaugmentation plot receiving oxygen and buffer, and up to 25% in the bioaugmentation plot receiving only buffer.
  • The presence and activity of JS666 was detected in bioaugmented plots but not in control plots, demonstrating the successful distribution of the bacterium. JS666 was also detected downgradient and transgradient from the injection wells in the bioaugmented plots but not in the upgradient or control wells.
  • The use of quantitative polymerase chain reaction (qPCR) and microcosm studies demonstrated that JS666 had spread and survived in the bioaugmented plots and was degrading cDCE. However, bacterial densities did not show consistent increases with time, making it challenging to conclude (1) whether growth was occurring and (2) the effect of oxygen on JS666 growth.
  • Cost Factors:
    To assess costs associated with bioaugmentation using the JS666 culture at a typical cDCE-contaminated site, a cost model was developed based on the pilot-scale treatment and was used to identify major cost elements. For this demonstration, total costs incurred were $323,900, as follows:

    • Capital costs (design and planning; well installation): $121,300
    • Operation and maintenance costs (groundwater amendments): $78,000
    • Performance monitoring, including baseline characterization: $124,600

    Description:
    The site is located in a former industrial area in the south-central portion of the SJCA Navy Depot in Chesapeake, VA. From 1849 to 1977, SJCA operated as a naval ammunitions facility. Currently, SJCA functions as a radar-testing range and also includes various administrative and warehousing facilities for the Norfolk Naval Shipyard. Historical uses at the site included machine, vehicle, and locomotive maintenance as well as equipment and chemical storage. Dumping of solvents and other chemicals for weed and dust control at the site has also been reported. These past activities along with the presence of two abandoned leaking USTs at a former fuel station on the site resulted in the release of VOCs to groundwater at the site. Based on historical records and field investigation data, a potentially favorable demonstration area was identified where (1) cDCE was present in higher concentrations and (2) moderately aerobic conditions were present. Groundwater samples collected in December 2007 indicated TCE, cDCE, and VC concentrations were less than 10 µg/L, 780 µg/L, and 2 µg/L, respectively at the demonstration area.

    The goal of this field demonstration was to evaluate the effectiveness of JS666 in biodegrading cDCE. Four test plots were constructed within the demonstration area. The first bioaugmentation plot received JS666, oxygen and buffer (Plot #1) while the second bioaugmentation plot receiving only the JS666 and the buffer (Plot #2). The remainder two plots served as controls. The first control Plot #3 received a buffer and the second control plot received both oxygen and the buffer (Plot #4) .The intent of the two bioaugmentation plots was to establish the effect of adding JS666 and additional oxygen on the rate of biodegradation, while the corresponding control plots were intended to account for the effects of buffer and oxygen on the results in the bioaugmentation plots. Two bioaugmentation events were performed during the demonstration, in October 2008 and February 2009. Monthly groundwater sampling results indicated that a greater reduction in cDCE was achieved in many of the wells in the bioaugmented plots compared to the control plots. However, the lack of oxygen and high levels of TCE in some parts of the demonstration areas inhibited the reduction of cDCE in the bioaugmented plots. As a result, the percent reduction was less than 75% relative to baseline concentrations.